The present invention relates to coil assemblies used for rotary electric machines such as magnet generator or magnet motor.
A conventional armature coil of this type, as disclosed in the specification of U.S. Pat. No. 3,091,715, comprises tabular half-coil conductors each including an inner portion, outer portion inclined radially and radial central portion provided by printed wiring on both sides of an insulating disc. A radial recess or slot is formed in the central portion of the half coil to divide each conductor into two branches, and a tongue of magnetic material is put to fill the recess thereby to increase the effective magnetic fluxes in the gap.
In the above conventional armature coil, when magnetic fluxes pass through the tongue of magnetic material in the axial direction perpendicular to the conductor, an annular eddy current is generated in the conductor on the outer periphery of the magnetic tongue, thereby leading to the disadvantage of the output being reduced by the eddy current loss.
Further, since the conductor is tabular in form and occupies a certain width in peripheral direction when arranged on the insulated disc, it is impossible to increase a number of winding turns, and therefore an output more than a predetermined level cannot be produced.